1. Field of the Invention
Since the advent of the horseless carriage, the commercial storage and dispensing of volatile fluids such as gasoline has been accomplished with very little concern. Typically, a steel tank, although more recently, fiber glass, often ranging from as little as 250 gallons to as much as 20,000 gallons, was unceremoniously dumped in a hole in the ground, and a pumping system connected to the tank permitted above ground dispensing of its contents.
Private users, such as, for example, farmers, often put a 55 gallon drum, or other storage vessel, on a stand above ground to permit gravity feed of the fuel.
Above ground storage of volatile fluids posed some unenviable problems, among them the likelihood that some fun loving hunter would find such tanks to be an irresistible target. Of course, those of a more vandalic character found such tanks to be a challenge. As a consequence, such tanks became a very real danger which subterranean tanks simply eliminated.
Moreover, since gravity exerted a constant force on the tanks' contents, leaks were not uncommon, and posed an immediate fire hazard not present in an underground installation.
In the past decade or so the public came to realize that underground tanks, not unlike their above ground counter-parts, corrode, and leak, too. Such leakage, however, goes sublimely unnoticed, unless or until the tank is pulled for one reason of another, or until contamination begins to appear in an adjacent water supply, or in the soil.
As a consequence of the myriad problems associated with the storage of volatile fluids, the Federal and State regulatory authorities have promulgated a definitive set of rules, codes and procedures regulating the installation, storage and dispensing of volatile fluids such as, for example, gasoline.
It is the principal objective of the present invention to provide a storage facility, above ground, which meets and exceeds all of the established criteria for such storage facilities, in the form of a storage vessel which is entirely compatible with the environment.
2. Overview of the Prior Art
Since the regulation of above ground storage of volatile fuels is a relatively new phenomenon, a search of the applicable prior art discloses correspondingly little in the way of proprietary concepts. In recognition of the danger inherent in storing volatile fluids, the use of double walled chambers has become vogue, but in and of itself, passe, for several reasons.
Double walled chambers typically interconnect at several points in order that the inner storage chamber can be supported by the outer chamber. Such interconnecting devices are almost uniformly heat conductive, and commonly electrically conductive. Thus, in the event of a fire, or an electrical strike, such as by lightning, or fallen electrical lines, the contents of the chamber, where there is typically some oxygen present, is a potential grenade.
Other than the convenience of it all, the value of an above ground tank is the ease with which leaks can be detected. However, mere detection is not protection against the leak itself, and concrete bases and shelters are often required to prevent spreading of leaked material, as well as to quell the temptation to shoot at it.
In reference to an essentially non-analogous art, such as in the area of storage of cryogenic fluids, double walled tanks are in common use. Such tanks invariably include insulation in what was before an air space between the walls. The focus of such construction was not for the purpose of preventing disastrous consequences of escaped volatile fuels, but rather to provide insulation in order to preserve the extremely low temperatures at which such liquids are stored.
Such is the import of Bradford U.S. Pat. No. 4,136,493 in which a double walled vessel employs an intermediate insulator material in the form of granulated perlite or vermiculite. 0f interest in Bradford is the claim by the inventor that the inner tank is fully supported by the insulation material. However, as is evident in FIGS. 3 and 4 of the patent, there is clear contact of a supportive nature between the platform 19, and the outer shell, which, in Bradford, is the wall of the excavation.
A similar device is disclosed in Hofmann U.S. Pat. No. 3,930,375, which, although earlier in time, embellishes on Bradford by employing a radiation shield and flecks of metal to act as radiation deflectors in the perlite.
Chemically inert cellular materials have been used in storing volatile fuels also, among them, various foams, and at least one effort to use concrete, but these efforts do not offer the spectrum of security and protection afforded by the present invention.